The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
In general, a vehicle with a dual clutch transmission (DCT) or a dual mass flywheel (DMF) has an external damper. Such a vehicle may cause a certain amount of noise when the engine is in an idle state.
We have discovered, that in a driving system in which an engine inertia portion, e.g., a primary flywheel, is connected to a sub-inertia portion, e.g., a secondary flywheel, with a damper, when the engine is in the idle state, a rotation speed (RPM: rotations per minute) may be changed due to torque disturbance generated in the engine. Accordingly, a difference of rotation speed between the engine inertia portion and the sub-inertia portion may be generated, and a resonance may be caused by the difference of rotation speed. The resonance frequency being generated is typically about 9 Hz, and, as we have discovered, the resonance frequency may cause the noise in the vehicle. The vehicle has DCT or DMF provided with the damper.
Therefore, conventionally, a structural method which increases connecting torque between the engine and the flywheel or hysteresis may be provided for reducing the noise. Further, a controlling method which increases the rotation speed when the engine is in the idle state is also provided for reducing the noise.
However, we have discovered that the above structural method may worsen a booming noise since the vibration of the engine is directly transmitted when the vehicle is launching or driving.
Meanwhile, according to the above controlling method which increases the rotation speed when the engine is in the idle state, we have discovered that fuel consumption and overall noise of the vehicle may be deteriorated.
The conventional controlling method in the idle state is as follows.
When the engine is in a cool condition and the idle state and an external load is applied thereto, a driving system of the engine may be vibrated. Thus, required correcting torque and an amount of the engine fuel may be changed together.
When the external load is applied when the engine is in the idle state, the engine driving system may be torsionally vibrated at the resonance frequency region as described above. Referring to the FIGS. 5 and 6, a rotation speed curve y1 of the engine inertia portion and a rotation speed curve y2 of the sub-inertia portion are inverse to each other. Therefore, in the conventional controlling method for a driving system, we have discovered the system is continually vibrated since the noise signal generated by the vibration above is applied as an input signal. In other words, the resonance frequency influencing the engine is not removed but continues.